Re: Re: [COMMITTERS] pgsql: Only try to push down foreign joins if the user mapping OIDs mat

Robert Haas <robertmhaas@gmail.com> writes:
> On Sun, Mar 13, 2016 at 10:51 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> I'm not really sold on enforcing that people create meaningless user
>> mappings.  For one thing, they're likely to be sloppy about it, which
>> could lead to latent security problems if the FDW later acquires a
>> concept that user mappings mean something.

> I think we should just fix build_simple_rel() so that it doesn't fail
> if there is no user mapping.  It can just set rel->umid to InvalidOid
> in that case, and if necessary we can adjust the code elsewhere to
> tolerate that.  This wasn't an intentional behavior change, and I
> think we should just put things back to the way they were.

So, allow rel->umid to be InvalidOid if there's no user mapping, and
when dealing with a join, allow combining when both sides have InvalidOid?
        regards, tom lane